Didn't the officer send a surrender and be boarded message when confronting both Enterprises? (Mandala Effect prevailing, time for me to have a rewatch

)
I agree that Trek did become succumb to Small Universe Syndrome (SUS) as it went on - even TNG was going to bring in Spock in season 2 (or was it the upright halo thing at the edge of the universe to have yet another time travel romp).
But this is one of the few times where having Worf showing up unexpectedly would have been a genuinely nice twist. Especially given season 3's storytelling style, it would not feel like SUS or leaning on TOS stories as a crutch to suss out... Worf growling and Dorn (okay, presumably) acting with much relish to villainously obliterate the Federation ships would have been a genuine hoot on top of everything else. (Dorn brought a ton into Worf's character, right down to disagreeing with the mandate Worf should have short hair. The Klingons would get worn out, but Dorn brought in a
lot to Klingon lore from day one that was worthy to be
combed fleshed out longer. That's what the best actor can do, embrace and extend a character. There's much to like, even in some of the less-successful episodes as standalone set pieces.)
Showing an evil Worf was a missed opportunity. And could easily have been better than the Yar/Castille shipping, which is easily the most cringeworthy part of the episode and would have flopped had season 3's style not been a part of it.